it entirely depends on the game you are playing, how it uses ram, and if there are any other bottlenecks in your system. Some games will benefit a lot from it, while others may not. AMD rigs will benefit from it more than an Intel rig due to how they interact with Ram.
1333 ram is budget ram and will not OC very far before having issues. To get to 1800 you would need 1600 rated ram or better to begin with. Another problem is that the higher the clock rate, the looser the timings, which eats into your real world benefit of the OC. Yes, it is not as much of as issue as it use to be, but it can still cause issues.
It is generally more likely to get more performance from a CPU or GPU OC, but the Ram may also need an OC to keep everything balanced.